Is my thermostat working properly?

[TurboDieselPoint]

Now that it has been below freezing for a couple of days, I have finally been using the heater and I noticed something I hadn't previously observed. Once the car is up to operating temperature (above 200*f), I can cool off the coolant temperature when I turn the heat to MAX with recirculation off and crank the fan speed to six with the engine idling. This evening it was 28*f outside, and with the engine idling and the heat on full as I described, the coolant temp went as far south as 180*f according to my Scangauge II in just a couple of minutes before I shut the engine off.

Seems to me the thermostat should prevent this from happening, but I'm not sure. Is this normal? Those of you with Scangauges, can you tell me if your car behaves this way also?

Thanks!

TurboDieselPoint

 

[Spyke]

Pretty normal.

Let me search for you the link.

I live in Montreal and every winter I get the same thing as you. Its normal.

 

[Spyke]

Technical product information
Engine temperature display fluctuates between 50° and 90° C - all TDI
Customer statement / workshop findings
At outside temperatures under 5°C the engine temperature fluctuates according to the display in the dash insert between 50 and 70°C or till the coolant temperature reaches 90°C. The phenomenon occurs mainly when driving at low engine speed.
Technical background
Because of a very good effectiveness of the engine in low rev range, little engine heat is passed on to the coolant. At low outside temperatures the coolant temperature does not reach 90°C. If the heating is used, the coolant loses further heat depending on the blower level. As a result, the coolant temperature can fluctuate between 50° and 90° C.
Below an outside temperature of 5° C and a coolant temperature of 70° C the standard PTC auxiliary heater is activated, to heat the interior.
Measure
Please do not repair, this is normal.
Customer information
A low coolant temperature has no effect on the service life of the engine. An engine oil with suitable viscosity is used.

 

[TurboDieselPoint]

Technical product information
Engine temperature display fluctuates between 50° and 90° C - all TDI
Customer statement / workshop findings
At outside temperatures under 5°C the engine temperature fluctuates according to the display in the dash insert between 50 and 70°C or till the coolant temperature reaches 90°C. The phenomenon occurs mainly when driving at low engine speed.
Technical background
Because of a very good effectiveness of the engine in low rev range, little engine heat is passed on to the coolant. At low outside temperatures the coolant temperature does not reach 90°C. If the heating is used, the coolant loses further heat depending on the blower level. As a result, the coolant temperature can fluctuate between 50° and 90° C.
Below an outside temperature of 5° C and a coolant temperature of 70° C the standard PTC auxiliary heater is activated, to heat the interior.
Measure
Please do not repair, this is normal.
Customer information
A low coolant temperature has no effect on the service life of the engine. An engine oil with suitable viscosity is used.

Thanks!

Where did you find this info? Now that you mention this, I remember reading a whole thread on here regarding coolant temps with the heater on. Have the link to the thread?

TurboDieselPoint

 

[VeeDubTDI]

That's very normal. Without load, the temp will drop off to the 180s when the heat is running. If it's really cold out (single digits), you can get into the 160s or even low enough to kick the electric heat back on. It's just really efficient, and contributes very little heat to the cooling system.

 

[Lightflyer1]

Temp this morning was 31F. Car only reached 181F after a 35 mile drive, with heat on and blowing. Fortunately Texas doesn't get much of this kind of weather. Where the mfd normally shows high 40's or low 50's mpg for my work commute, this morning was only in the low 40's. Normal car temp is around 203F when warmed up.

 

[Spyke]

Thanks!

Where did you find this info? Now that you mention this, I remember reading a whole thread on here regarding coolant temps with the heater on. Have the link to the thread?

TurboDieselPoint

I received that info fron volkswagen canada when the dealer sent an email because they couldn't figure out why my coolant temp was fluctuating after changing the coolant 3 times, the thermostat and another sensor.

 

[nord]

Our little TDI's have more issues retaining heat than shedding it. Bear in mind that the diesel is a fuel-controlled engine versus an air-controlled gasoline type. Thus a diesel spends most of its life running lean.

Unlike a gasoline engine where a lean burn causes excessive heat and possible damage, the diesel just makes a smaller bang and runs cooler. Less shed heat means more efficiency but also means less available heat for creature comforts.

I might suggest that a winter front be considered if this becomes a real issue. The more you bundle a TDI in winter conditions the better it will retain heat. Two benefits here... You'll be warmer and the diesel will be happier as it will better stay in an optimum operating temperature range.

 

[kydsid]

Hell when I lived up north gas cars would do that, just has to be a little colder.

 

[VeeDubTDI]

On my 8 mile drive home the other day it didn't even make it up to 165.

 

[tdiatlast]

More of the same: 30 minutes, 29f ambient, stop-and-go traffic, 166-168f scangauge II.

 

[czeetah]

I can cool off the coolant temperature when I turn the heat to MAX with recirculation off and crank the fan speed to six with the engine idling.

Heck, this was one of the things my Dad taught me when I was learning to drive. Keep an eye on coolant gauges, if something happens and it starts getting hot turn on the heat and and fan to max to see if that helps enough to get you not stranded on the side of the road.

Actually helped me once or twice in my life when a thermostat didn't stick shut totally.

Standard effect. Put hot water in heat exchanger and blow air over it, temperature of hot water will decrease.

It's basically like a little mini-radiator in your dashboard.